Magnesium- and intermetallic alloys-based hydrides for energy storage: Modelling, synthesis and properties

Hydrides based on magnesium and intermetallic compounds provide a viable solution to the challenge of energy storage from renewable sources, thanks to their ability to absorb and desorb hydrogen in a reversible way with a proper tuning of pressure and temperature conditions. Therefore, they are expected to play an important role in the clean energy transition and in the deployment of hydrogen as an efficient energy vector. This review, by experts of Task 40 'Energy Storage and Conversion based on Hydrogen' of the Hydrogen Technology Collaboration Programme of the International Energy Agency, reports on the latest activities of the working group 'Magnesium- and Intermetallic alloys-based Hydrides for Energy Storage'

Research and development of hydrogen carrier based solutions for hydrogen compression and storage

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Completely Elastic Deformation of Hydrogenated Ta Thin Films

Nanostructured metal hydrides could play a key role in a hydrogen economy. The nanostructuring or confinement of these materials as, e.g., thin films significantly affects the structural and functional properties. For tantalum hydride, a versatile hydrogen sensing material, we show that the confinement of tantalum as a thin film extends the solubility limit by suppressing the phase transition observed in bulk upon hydrogenation. Different from bulk, the body centered cubic unit cell continuously deforms with unequal lattice constants and angles between lattice vectors. This deformation ensures that the volumetric expansion is realized in the out-of-plane direction, and surprisingly, completely elastic in nature. The first-order phase transition suppression combined with the continuous elastic deformation of the tantalum unit cell over an extraordinary wide solubility range ensures the superb performance of tantalum and its alloys as a hysteresis-free optical hydrogen sensing range over a hydrogen pressure/concentration range of over 7 orders of magnitude.</p

In situ X-ray diffraction under H2 of the pseudo-AB2 compounds: YNi3.5Al0.5Mg

The hydrogenation and dehydrogenation behaviours of the YNi3.5Al0.5Mg compound were studied by in situ X-ray diffraction under hydrogen pressure and at room temperature. The changes of (i) the lattice parameters, (ii) the crystallite size and (iii) the lattice strain during the sorption process (i.e. along the PC isotherms) were studied. These results indicate that the crystallite size decreases by a factor of 2. The micro deformations increase at first and then tend to almost zero at the end of the sorption cycle. This behaviour is explained in terms of co-existence of the metal (i.e. greek small letter alpha phase) and metal hydride (i.e. β phase) phases. The change in crystallinity is consistent with the hydrogen induced amorphisation process existing in a lot of AB2 compounds. No anisotropic effects can be highlighted on this pseudo-AB2 compounds in contrary with what could be observed in AB5 compounds

Development of in situ synchrotron X-ray total scattering setup under pressurized hydrogen gas

We have developed an in situ gas‐loading sample holder for synchrotron X‐ray total scattering experiments, particularly for hydrogen storage materials, designed to collect diffraction and pair distribution function (PDF) data under pressurized hydrogen gas. A polyimide capillary with a diameter and thickness of 1.4 and 0.06 mm, respectively, connected with commercially available fittings was used as an in situ sample holder. Gas-leakage tests confirmed that this sample holder allows 3 MPa of hydrogen gas pressure and 393 K to be achieved without leakage. Using the developed in situ sample holder, significant background and Bragg peaks from the sample holder were not observed in the X‐ray total scattering patterns and their signal‐to‐noise ratios were sufficiently good. The results of Rietveld and PDF refinements of Ni powder are consistent with those obtained using a polyimide capillary (1.0 mm diameter and 0.04 mm thickness) that has been used for ex situ experiments. In addition, in situ synchrotron X‐ray total scattering experiments under pressurized hydrogen gas up to 1 MPa were successfully demonstrated for LaNi4.6Cu

Reaction paths via a new transient phase in non-equilibrium hydrogen absorption of LaNi2Co3

放射光その場X線回折測定によりAB5型LaNi2Co3の非平衡な水素吸蔵反応過程を調べた。2つの水素ガス導入圧力で1秒毎にX線回折パターンの測定を行った。1MPaの導入圧力では以前の平衡状態での測定では観測されていない過渡的な状態への変化が観測された。この状態は高水素組成（x~4.5-5.5）の水素化物へ続いて変化するが、平衡状態で出現する水素組成の相（x~3.6）は出現しない。0.18MPaの導入圧でも初めに過渡的な状態が出現するが、その後にx~3.6の水素化物相へ変化し、最終的に高水素組成の水素化物相へ変化する。この結果は高い導入圧力では過渡的な状態の形成が促進され、固溶体相と過渡的状態への水素の溶解が増大することで高水素組成相への連続的な変化が助長されることを示している